1. Field of the Invention
The present invention relates to a paper stacking apparatus for stacking a large amount of recording paper output from a printer or the like for a host computer, and more particularly to such a paper stacking apparatus capable of preventing break of a paper stacked condition possibly occurring in stacking different-sized sheets of paper in a mixed condition.
2. Description of the Related Art
A high-capacity paper stacking apparatus connected with a printer or the like for a host computer is designed to stack printed sheets of paper having various sizes continuously ejected from the printer, on a paper stacking tray in order of ejection of the printed sheets.
A typical paper stacking apparatus of this kind will now be described. Each printed sheet of paper ejected from the printer is first received by a disk provided in the paper stacking apparatus and is then stacked on the paper stacking tray by rotation of the disk. The paper stacking tray is lowered according to an amount of paper stacked thereon and is controlled to be located always in a proper position allowing receipt of the paper from the disk. In such a position control of the paper stacking tray, an elevator motor for vertically moving the paper stacking tray is controlled to be driven in relation to presence or absence of paper on the paper stacking tray and rotating operation of the disk, that is, paper ejecting operation of the printer, thereby lowering the paper stacking tray by a given distance to the proper position. In this manner, every time a given amount of paper is stacked on the paper stacking tray, the lowering of the paper stacking tray by the given distance is repeated to effect stacking of a large amount of paper on the paper stacking tray.
However, in a conventional paper stacking apparatus having no paper guide as disclosed in Japanese Utility Model Laid-open No. Hei 2-69665, for example, stacking of a large amount of paper brings about break of a paper stacked condition on the paper stacking tray. For example, when a large amount of paper having a small size is first stacked and a large amount of paper having a large size is then stacked on the stack of the small-sized paper, the large-sized paper projects from the outline of the small-sized paper to cause the break of the paper stacked condition. Further, in a conventional paper stacking apparatus as shown in FIG. 10 of Japanese Patent Laid-open No. Hei 4-251070, no paper guide is provided in a paper ejecting direction, so that when a large amount of paper having a small size in the paper ejecting direction is first stacked and a large amount of paper having a large size in the paper ejecting direction is then stacked on the stack of the small-sized paper, the large-sized paper projects from the edge of the small-sized paper in the paper ejecting direction to cause the-break of the paper stacked condition. Further, in a conventional paper stacking apparatus as shown in FIG. 2 of Japanese Patent Laid-open No. Hei 1-198766, paper guides are provided in a paper ejecting direction and in a lateral direction perpendicular to the paper ejecting direction, so that there is no possibility of the break of the paper stacked condition when stacking paper having the same size as a size defined by the paper guides. However, when a large amount of paper having a small size is first stacked and a large amount of paper having a large size is then stacked on the stack of the small-sized paper, there is a possibility of the break of the paper stacked condition.